Before the Internet, airlines had to be called individually and asked for their best rates. Calling every airline and comparing their prices was a very long and drawn-out process. But now you have the ability to easily compare flight prices online using a variety of websites dedicated to cheap travel. When you finally do go on your trip after buying your flight tickets online, you can rest easy knowing that you did all the research you could to find the very best airline rate.
Go to Orbitz.com and enter in your flight details. Orbitz is helpful for comparing flights because it gives you a listing of all of the major airlines side by side for comparison. You can also choose a "flexible date" search where you give a range of dates that you are willing to travel within for a cheaper flight.
Go to Hotwire.com and do a search for the cities you want to travel between. Keep in mind that Hotwire requires you to pay for your flight in advance in exchange for lower rates and there are no refunds or changes allowed. Hotwire helps you out by suggesting airports near your chosen city that could be a much less expensive option for your trip.
Visit Expedia.com to find a flight with a flexible stay. Expedia also has a travel rewards program that will allow you to accrue points towards travel or gifts whenever you book your flight at this website, so keep this in mind when you're comparing your final options.
Search Travelocity.com's low deals and low fare alerts section to see if you can find a really good rate on a flight to your desired city.
Submit an offer on Priceline.com for the flight of your choice. Below the standard search is an option to "bid now." Tell it what you want to pay for your flight. If you pay the "Name Your Own Price" bid and within 24 hours find an even lower fare, it'll give you back the difference.
Narrow your findings down to the least expensive options and then compare them further. Which options have the least number of stops? How early in the morning or late at night will you have to travel? Are there any additional fees charged by the airlines (outside of the price quoted on the website) that you will have to pay at the airport such as baggage or food fees? Compare the reviews that both the airlines and the flight quote sites have received from customers.